TRAILER MANFD 1960 THRU 1962.POSSIBILITY THAT INDUCTION HARDENING PROCESS INEFFECT AT NORTH-AMERICAN ROCKWELL'S AXLE PLANT MAY HAVE CREATED HIGH RESIDUALSTRESSES AT INNER BEARING SHOULDER AREA STRESSES MAY TURN INTO PHYSICAL CRACKSUNDER EXTENDED FIELD SERVICE.CONTINUED USE OF AXLE AFTER CRACKING MAY CAUSEAXLE SPINDLE TO FRACTURE.(CORRECT BY INSPECTING ANDREPLACING WITH NEW AXLE.)